This application relates to a method and apparatus for the non-invasive, quantitative measurement of physiological chemicals, particularly glucose, in a patient.
Determination of blood glucose is a routine procedure performed several times a day by many diabetics. In general, this procedure involves the taking of a small blood sample and evaluating the level of glucose in the sample. Common instruments used for this purpose use the enzyme glucose oxidase to convert glucose and oxygen to gluconic acid and hydrogen peroxide, and then measure the level of peroxide by either spectroscopic or electrochemical means.
While these daily measurements provide the diabetic patient with the ability to self-monitor and thus better control blood glucose levels, they are not without drawbacks. In particular, the taking of blood samples several times a day can be painful and exposes the patient to a risk of infection. Moreover, using this existing technology it is impossible to obtain a continuous blood glucose measurement. Thus, during the night, a patient must either be awakened periodically for testing or run the risk that glucose levels will drop to dangerous levels as they sleep.
In view of the foregoing, there exists a real need for a non-invasive method of measuring blood glucose in a patient. It has been suggested that this could be accomplished using near-infrared (NIR) radiation. Thus, U.S. Pat. No. 5,086,229 of Rosenthal, which is incorporated herein by reference, describes a system using a plurality of infrared light emitting diodes and a detector to measure blood glucose. The infrared measurement of glucose in the body is immensely complicated, however, because of the substantial absorbances of fats and proteins in the near-infrared. Thus, while the Rosenthal patent presents an interesting theory, there is no published documentation that demonstrates the ability of the Rosenthal system to measure glucose noninvasively. Furthermore, the wavelengths used in the Rosenthal system have never been shown to possess useful glucose information.
It is an object of the present invention to provide a practically useful non-invasive near-infrared detector for blood glucose and other physiological chemicals that is adaptable for continuous use.
It is a further object of the present invention to provide a method for the non-invasive quantitative measurement of physiological chemicals and particularly glucose in a patient that can be used either continuously or intermittently.
It is still a further object of the invention to provide an apparatus for continuous or intermittent non-invasive monitoring of blood glucose and other physiological chemicals in a patient.